FR2486663A1 - FLEXIBLE OPTICAL CONDUIT AND METHOD OF MANUFACTURING THE SAME - Google Patents

Abstract

A FLEXIBLE BEAM FOR CONDUCTING IMAGES IN THE FORM OF OPTICAL FIBERS IS PRODUCED BY JUXTAPOSING AND STRETCHING A SERIES OF FIBERS OF GLASS 20 SHELLS OF EXTRACTABLE GLASS. THE STRETCHED ASSEMBLY IS CUT TO THE DESIRED LENGTH AND THE INTERSTITIAL GLASS RODS 22 ARE EXTRACTED FROM THE PART OF THE CUT PART. APPLICATION TO THE MANUFACTURE OF INDUSTRIAL AND MEDICAL ENDOSCOPES.

Description

The present invention relates, in general, to a flexible conduit

  in image-conducting fibers and, more particularly, improvements made to the beam bundles

  optical fibers isolated by extraction with a sol-

  and their process of preparation. The known methods for manufacturing flexible ducts

  image carriers extracted with a solvent

  have secondary gains in acid-soluble glass

  surrounding optical fibers or fins made of

  ble in acids projecting radially from these fibers. As examples, US patents

  Nos. 3,624,816 and 3,653,739 describe such methods.

  Where secondary glass ducts are provided

  extractable on the fibers, we observe, because of the

  many additional interfaces between the multi-component

  plies added to achieve these secondary sheaths and resulting surface areas exposed to the

  contamination, a reduction in the optical quality of the product.

  For example, contamination by foreign bodies of the various components promotes the formation of bubbles at

  interfaces, which bubbles affect the essential surfaces

  the conductors of fiber light during

  rations of breath. In addition, the choice of glasses used

  for the manufacture of fibers consisting of three

  res is limited to combinations with compatibility

  stretching ability, that is to say that the glasses must

  have temperatures and dilatation properties

lar.

  In the case of fusion of extractive glass fins

  acid on the primary fiber sheath, as described in US Pat. No. 3,653,739, the manufacture of

  fibers is extremely tedious, inconvenient and costly

  Teuse. It follows that the advantage that we draw on the plan

  the reduction of the alteration of the fiber core is con-

  overwhelmed by the difficulties and cost of manufacturing. In view of the foregoing, the present invention aims to simplify and reduce the cost of manufacturing

  flexible fiber optic conduits isolated by extraction.

  More particularly, the invention proposes to

  to overcome the limitations of the hitherto long and costly manufacturing processes, and its aim is to improve the quality of

of the product.

  It also aims to achieve the above goals by offering greater freedom in the choice of

glass systems.

  Other objects and advantages of the invention will emerge

of the following description.

  The extracted fiber optic conduit is produced, se-

  According to the invention, by juxtaposing a selected series of preformed elements of conventional sheathed optical fibers and rods.

  interstitials in glass soluble in acids. Preferably

  the rods are arranged in such a way in the interstices and are of such a diameter as to prevent them

  any contact between the preformed fiber elements.

  The assembled components are heated and stretched as a unit having the desired reduced cross-sectional area for the optical fiber final conduit, after which they are cut to the desired length. The cut section is

  then subjected to an extraction which eliminates the

  titiels to give the duct the desired flexibility.

  This process improves the quality of the obtained fiber bundle, simplifies the manufacturing process and offers an unusual freedom in the choice of glass compositions

  and combinations used in the system.

  The invention is described in detail with reference to the accompanying drawings in which:

  - Figure 1 shows, in perspective, a form of execution

  flexible fiber optic conduit formed according to the

  vention; Figure 2 is an end view of a preformed component element used to produce the conduit of Figure 1; FIG. 3 schematically illustrates the stretching and cutting operations according to the invention; - Figure 4 is a cross-sectional view taken on. inq of line 4-4 of Figure 3; - Figure 5 illustrates a subsequent step of the manufacturing method according to the invention; and - Figure 6 is a sectional view taken along the

line 6-6 of Figure 5.

  Flexible fiber optic conduits having

  opposing menses formed of constituent fibers arranged according to the same geometrical pattern are used as trans-

  image carriers in various forms of industrial endoscopes

  triels and medical. Usually, these devices include

  a lens adjacent to one end of the fiber optic conduit and an eyepiece adjacent to the opposite end of the conduit, the first to form the images to be transported and the second to facilitate examination

  images carried by the conduit.

  The invention relates to the manufacture of a conduit in

  As a product per se, and as a result, its use or ability to enter the composition of various forms of EddOeopes or the like will not be discussed in detail. It is well known, however, that the requirements for flexible fiber ducts

  exceptionally small diameter optics and having

  thin fiber can be more easily achieved by using fiber extraction techniques, this process can also be used for the manufacture of

ducts of larger diameter.

  The extracted optical fiber duct, whether of large or small diameter and whether the size of the fibers is large or small, is illustrated in the form of the bundle of

  fibers 10 (figure). The fibers 12 of the bundle 10 are closely

  merged together or in any other similar manner at their opposite ends 14 and 16,

  one or other of these ends can serve as extremes

  receiving image in the beam. The fiber portions 12 between opposite ends joined together are free to flex separately and independently

each other.

  The fiber bundle 10 is produced from an element

  preformed 18 (FIG. 2) which comprises an ordered assembly

  born of cylindrical sheathed elements 20 from which the

  12 fibers are produced and interstitial spacing rods

  22 made of a material soluble in acids.

  The elements 20, having a core 24 of refractive index

  and a sheath 26 having a refractive index relative to

  low, are concentrically arranged around a

  20a, which gives the preformed element 18 a generally circular cross section. Alternatively the elements 20 could be arranged in successive rows

  to give a rectilinear preformed element 18.

  While it is true that the cross-sectional size of the acid-soluble elements and rods 22 may be varied, it is preferred that the rods 22 be of such a size and viscosity as the fiber draw temperature they prevent the elements from coming into contact with

  each other, while creating spaces 28 (Figure 4),

  releasing gas during drawing of the element

preformed 18 (Figure 3).

  The usual method of drawing multiple fiber bundles is to heat the preformed element 18 by heating, for example by means of electric heating coils, and to stretch it longitudinally so as to bring it to a reduced cross-section corresponding to that wanted to

  beam 10. This may require several labeling operations.

  rage or a single operation may suffice.The technique of stretching

  ge illustrated in Figure 3 is applicable in both cases.

  If we consider that FIG. 3 represents the final stretching phase, the stretched section 32 of the preformed element

  18 is cut to the desired length Lq and then provided with a

  34 of wax or other acid-resistant material at each end and immersed in an extraction solution.

  36 (Figure 5) for the removal of the glass rods

22.

  As shown in FIG. 4, the fibers 12 formed by the stretching operation of FIG.

  interstitial matrix 38 which retains the transverse geometry

  initial dirty of the preformed element 18 throughout the

  stretched section 32. The die 38 is formed of the heated material

fé and stretched rods 22.

  Extraction, as shown in Figures 5 and 6

  releases the fibers 12 which gives the beam 10 the flexibility

  expected, while retaining the initial geometric distribution of the fibers making up the opposite ends of the beam. These ends of the bundle 10 may be compacted if desired, for example closely juxtaposed by a treatment similar to that described in United States Patent No. 3,669,772.

  Examples of glasses that can be used for the manufacture of

  components of the core and sheath of the elements 20 from which the fibers 12 are formed, it is possible to quote

  respectively flint and crown glasses. The glasses

  The core and sheath usually have a refractive index of 1.75 and 1.52. Of course, it is within the abilities of those skilled in the art to choose other glasses and combinations

  refractive indices. The components of heart and happiness

  elements can be either prefused or simply

  assembled and not fused into the preformed element 18.

  In both cases, their final fusion occurs during the stretching.

fiber age 12.

  The materials likely to form the intersecting rods

  The metals 22 may be metals, for example aluminum, but they are preferably glass having a high boron content and which are soluble in acids. The borosilicate glasses mentioned in US Pat. No. 3,004,368 are suitable for this purpose, but acid-free silica-free glasses are preferred. A suitable composition comprises approximately 47% by weight tricKdede boron, 45% by weight barium oxide; and 8% by weight of lanthanum oxide. As an extraction solution 36

  can be used for the materials constituting the transverse rods

  Examples 22 include sodium hydroxide for aluminum

  and hydrochloric acid for boron glasses.

  Extraction of the composition cited as an example can

  be easily performed using a solution formed of

  approximately 5% by volume of hydrochloric acid maintained

  approximately 650C. The acid concentration and the temperature

  the temperature at which extraction is performed can be

  variously regulated by the skilled person.

  It is understood that the invention is not limited to the embodiment described and shown and that one

  can make various modifications and adaptations

  without departing from the scope of the invention. -

Claims (6)

  1-Process for manufacturing a flexible conduit made of image-conducting fibers, characterized in that it consists of:   to achieve a preformed element 18 consisting of a   of fibers by juxtaposing a series of glass-sheathed optical glass elements and interstitial rods 22 into   extractable material, which rods 22 serve to   ter said elements 20 from each other; - heating and stretching said preformed element 18 into a cross-sectional dimension approximately corresponding to that desired for said conduit, said rods 22 creating an interstitial matrix 38; a cut, in said stretched section 32, a length L which coriEspord the desired length for said conduit; covering the opposite ends 14 and 16 of said cut length L of said stretched section 32; and   - to submit the uncovered parts of the said lon-   1 of stretched section 32 to an extraction medium 36   sufficient time to eliminate the said matrix interstitial 38.   2. Process according to claim 1, characterized in that   glass-sheathed glass elements are formed each   cun of a heart 24 conductor of light and offering a   high refractive index and a sheath 26 surrounding said   The core has a relatively low refractive index.   3. Process according to claim 2, characterized in that   that the sheaths 26 are fused to said core 24.   4. Process according to claim 1, characterized in that   that the interstitial rods 22 are soluble in acids.   - Process according to claim 4, characterized in that said extraction medium 36 is a hydrochloric acid solution.   6- Flexible Conductive Fiber Conduit Image, Characteristic   characterized in that it comprises a series of juxtaposed light-conducting fibers 12 having opposite ends 14, 16 arranged in a similar geometric distribution and a matrix 38 formed of a series of rods 22, which matrix gathers the component fibers together. the respective opposite ends 14 and 16, the fiber portions 12 between said ends 14 and 16 being devoid of said die 38 and able to flex indefinitely each other.   7- Flexible conductive fiber conduit images according to claim 6, characterized in that said fibers 24 are glass and they are individually sheathed glass. 8 - Flexible duct fiber conductive images according   Claim 7, characterized in that the matrix 38 forms   of a series of rods 22 is a soluble glass in   fused on the glass fiberglass 24.